The present invention broadly relates to molding devices and, more specifically, pertains to a new and improved construction of a device for pressure-aided molding, especially injection molding of shaped or three-dimensional bodies.
In its more particular aspects, the invention concerns a device for pressure-aided molding, especially injection molding, of shaped bodies from high-molecular molding massive, especially polymers, such as synthetic rubber, natural rubber or latex, thermoplastic plastics and the like, and which bodies are preferably of small dimension. The device comprises at least one preparation chamber, especially a plasticizing chamber, comprising at least one rotatably driven conveying or transporting and mixing screw conveyor, especially a plasticizing screw conveyor arranged within the preparation chamber and having a transport direction and an axis of rotation. The device also comprises at least one charging port for filling the at least one preparation chamber with at least one preferably thermally plasticizable, possibly molecularly cross-linkable mass, especially a polymer, pre-polymer and/or a component of at least one polymer. The preparation chamber makes a pressure-tight transition into at least one storage chamber for plasticized polymer. The storage chamber, in turn, opens into at least one mold cavity filling conduit, preferably an injection molding channel, for charging at least one mold part of a mold or the like with the plasticizable molding mass. The, and preferably all, above-mentioned components or elements may be temperature adjustable. A device comprising a drive means, for instance a fluid medium drive means, is also provided. This drive device is provided for accomplishing translatory-relative motions of the preparation chamber and the mold cavity filling conduit, especially the injection molding channel, preferably in the direction of the axis of rotation of the transporting and mixing screw conveyor. The molding device can be especially advantageously employed for the fabrication of shaped bodies or three-dimensional bodies of small dimensions.
In other words, the device of the present invention is for pressure-aided molding, especially injection molding, of shaped or three-dimensional bodies having high-molecular masses, especially polymers such as synthetic rubber, natural rubber or latex, thermoplastics and the like, and which bodies are preferably of small dimension. The molding device comprises a preparation chamber defining a plasticizing chamber, at least one rotatably driven transport and mixing screw conveyor defining a plasticizing screw conveyor arranged within the preparation chamber and having a predetermined transport direction for the molding mass and a rotational axis and at least one charging port for filling the preparation chamber with at least one plasticizable molding mass. The preparation chamber makes a pressure-tight transition into at least one storage chamber for plasticized polymer. The molding device also comprises at least one mold cavity filling conduit for charging at least one mold cavity of a mold or the like with the molding mass. The storage chamber opens into the at least one mold cavity filling conduit. The, and preferably all, above-mentioned elements may be temperature-regulatable. The molding device also comprises a drive means. The drive device serves for accomplishing translatory-relative motions of the preparation chamber and the mold cavity filling conduit. This drive device is associated with the preparation chamber defining the plasticizing chamber and at least one prolongation or extension thereof. The drive device is associated with at least one storage chamber arranged subsequent to the preparation chamber in the transport direction of the transport and mixing screw conveyor and exhibits an inner wall with substantially mutually parallel generatrices.
From German Pat. No. 1,779,239, an injection molding device possessing a dosage or metering cylinder is known whose one end has a molding or injection opening which can be applied to the opening of an injection mold and in whose other open end, the end of a pressure piston constructed as a hollow piston can be translatably guided. An axially translatable conveying screw is mounted in the pressure piston. The axially translatable conveying screw is rotatable and is equipped with a displacement device which exerts an axial thrust on the axially translatable conveying screw in the direction of the dosage or metering cylinder. There are also provided stops for limiting the movement of the movable pressure piston during injection molding. It is thus known to fill at least one preparation chamber, especially a plasticizing chamber, comprising at least one rotatably driven conveying or transporting and mixing screw conveyor, especially a plasticizing screw conveyor, through at least one charging port with preferably thermally plasticizable, possibly molecularly cross-linkable polymer, pre-polymer and/or the components of at least one such polymer. Furthermore, in this arrangement the preparation chamber makes a pressure-tight transition into at least one storage chamber for the plasticized mass. The storage chamber opens into at least one mold cavity filling conduit, preferably an injection molding channel, for charging a mold part of a mold or the like with a mass to be molded. Preferably, all above-mentioned components are temperature adjustable. The known molding device also comprises a drive means, for instance a fluid medium drive means. This drive device also is provided for translatory-relative motions of the preparation chamber and the mold filling conduit, especially the injection molding channel, preferably in the direction of the rotational axis of the screw conveyor.
It is furthermore known, when injecting plastic masses, to move a substantially non-translatable screw conveyor located in the preparation chamber in a piston-like manner together with the preparation chamber into the storage chamber. The disadvantage of such a construction is that the body comprising the storage or transfer chamber and the injection channel connected to this body possesses an inner cross-section which must be substantially at least as great as the outer cross-section of the plasticizing cylinder possessing the conveying screw or screw conveyor. Especially during the fabrication of small components which require smaller injection volumes it is necessary, due to the large transfer-space cross-section, to keep the path of the piston formed by the conveying screw cylinder and conveying screw short during the injection molding procedure. In order to achieve a very exact dosing or charging as is required by injection molding, the control and regulation expenditure is high for precisely maintaining such a slight stroke during the injection molding procedure. In addition, susceptibility to breakdowns cannot be entirely avoided.
It is furthermore known to move an axially translatable, rotatably journaled conveying screw or screw conveyor located in the preparation chamber or plasticizing chamber through the stroke of the injection molding procedure in a piston-like manner within the preparation chamber or plasticizing chamber.